Affirmative action is racist, that cannot be denied as it is using race as one of the selection criteria, unfortunately it is also a necessary evil.
While saying it is not necessary and unfair for whites, and that we should live in a meritocracy, one must never forget that we live in a world full of racist assholes. The role of affirmative action may not seem like much in America, but in South Africa it is racist to the extreme but also completely necessary. In South Africa the majority of employers are white and if they were allowed to they would also only hire white people. Even with Affirmative action in place this is still the most common occurrence, despite black applicants vastly outnumbering white applicants.
Affirmative action does marginalize whites to a degree. In South Africa it is completely impossible for a 50+ year old white male to get a job, and one of the reasons for that is affirmative action. As a result Affirmative action does perpetuate racism. However, one must realize first that racism cannot be magically abolished. People are racist, and many use that racism in decision making. Affirmative action hopes to level the playing fields for the more traditionally marginalized members of society, the vast number of who were prevented from getting jobs as a result of race.
Like I said affirmative action is racist, but a necessary evil. especially since economic levels between racial groups are still so different. As time allows for the differences between race groups to minimize then systems like affirmative action can begin to be scrapped. However until then, it is unfortunately necessary.